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Configuring Exchange plus second mail server for one domain

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  • Configuring Exchange plus second mail server for one domain

    I have a Small Business Server 2003 with Exchange setup for our primary domain. I'd also like to run a second mail server on our web host (Apache) for POP mailboxes I don't want to have on the Exchange server.

    I've run across this MS article ( which discusses sharing SMTP address space, which seems to get close but am unsure what I'm doing wrong.

    I've got two DNS MX entries ( [10] pointing to the Exchange server, and [20] pointing to the POP server on the web host). I've setup additional mailboxes on the POP server and they can send out, but any mail sent to those POP addresses get returned with 550 errors (not here).

    I'm assuming this means that the Exchange server is killing the emails since it doesn't have the mailboxes instead of forwarding them onto the second mail server for handling. I've checked Exchange's settings as recommended in the above article and the This Exchange Organization is responsible for all mail delivery to this address check box is selected and greyed out so I can't change it.

    I think I need to configure the Exchange server so it relays any requests for boxes that it doesn't control to the other, POP, server, but am not sure how to setup the relaying correctly. I know there are relay issues that can get our server blacklisted so I want to configure this the right way.

    Can anyone tell me what I'm doing wrong, or better, link me to a procedure where I can follow the steps to set this up corretcly?

    Thank you in advance for the help.

  • #2
    Re: Configuring Exchange plus second mail server for one domain

    First of all, you only need one MX record pointing to your Exchange server, since it is "authoratative" for your domain. A secondary MX should point to a backup mail server - one that can hold your mail whilst Exchange bis unavailable.
    Once all mail is routed to your Exchange, you follow that KB to the letter so that any unresolved addresses get forwarded to the POP3 server.
    Take it from there.

    Steven Teiger [SBS-MVP(2003-2009)]
    Iím honoured to have been selected for the SMB 150 list for 2013. This is the third time in succession (no logo available for 2011) that I have been honoured with this award.

    We donít stop playing because we grow old, we grow old because we stop playing.


    • #3
      Re: Configuring Exchange plus second mail server for one domain

      As teiger says, secondary MX is for a backup mail host. Messages only get delivered to one MX host.

      I'm not sure what your specific requirement for having the POP3 an entirely separate machine is though, can you not get away with turning on the POP3 service on Exchange and use that?

      If you don't want your Exchange users to see them, change the hide from address lists section in the user properties. It'll make things a lot less complicated in the long run having everything in one place..